A solution of tert-butyl ((1S)-3-chloro-2-oxo-1-{[(3S)-2-oxopyrrolidin-3-yl]methyl}propyl)carbamate (1.26 g, 4.3 mmol) in dichloromethane (107 mL) at 0 °C under nitrogen was treated with 48% hydrobromic acid (0.48 mL, 4.3 mmol) with effervescence observed. The reaction was stirred at 0 °C for 1 h, washed once with water (30 mL), dried over MgSO4, filtered, and concentrated to afford 1.23 g (83%) of the title compound as a white solid. 1H NMR (400 MHz, DMSO-d6) δ 7.64 (s, 1H), 7.51 (d, J = 8 Hz, 1H), 4.46 (d, J = 16 Hz, 1H), 4.41 (d, J = 16 Hz, 1H), 4.19 (m, 1H), 3.13 (m, 2H), 2.26 (m, 1H), 2.13 (m, 1H), 1.87 (m, 1H), 1.63 (m, 2H), 1.38 (s, 9H); MS (ESI+) for C13H21BrN2O4m/z 371.0 (M + H)+.